1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
#include <bits/stdc++.h>
using namespace std;

int a[50005];

int main()
{
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    int n;
    cin >> n;
    for (int i = 1; i <= n; i++)
        cin >> a[i];
    
    int ans = 1e9, cur = 0;
    for (int i = 1; i <= n; i += 2)
    {
        if (i != 1 && a[i - 1] >= a[i])
        {
            cur++;
            continue;
        }
        if (i != n && a[i + 1] >= a[i]) cur++;
    }
    ans = min(ans, cur);
    cur = 0;
    for (int i = 2; i <= n; i += 2)
    {
        if (i != 1 && a[i - 1] >= a[i])
        {
            cur++;
            continue;
        }
        if (i != n && a[i + 1] >= a[i]) cur++;
    }
    ans = min(ans, cur);
    cur = 0;
    for (int i = 1; i <= n; i += 2)
    {
        if (i != 1 && a[i - 1] <= a[i])
        {
            cur++;
            continue;
        }
        if (i != n && a[i + 1] <= a[i]) cur++;
    }
    ans = min(ans, cur);
    cur = 0;
    for (int i = 2; i <= n; i += 2)
    {
        if (i != 1 && a[i - 1] <= a[i])
        {
            cur++;
            continue;
        }
        if (i != n && a[i + 1] <= a[i]) cur++;
    }
    ans = min(ans, cur);

    cout << ans;
}